1. Field of the Invention
This invention in general relates to photographic processing systems of the type used to spread a fluid processing composition in a thin layer between selected elements of self-processable type film units while simultaneously advancing such film units to the exterior of a camera and in particular to a method by which the assembly of such processing systems is facilitated through the use of an adjustable electric discharge machining technique used to partially texture rollers utilized in such systems.
2. Description of the Prior Art
Highly automated photographic cameras which utilizes integral self-processable type film units are well known in the photographic field, having been extensively described in the patent literature and in public use for several years now. Such cameras are designed to automatically produce finished, waste-free color prints with virtually no operator involvement other than to compose the picture, perhaps focus, and then actuate the camera by depressing its cycle "start" button.
Such cameras accomplish this through the use of specially-designed camera subsystems that are structured and logically organized to carry out a programmed series of sequential operations which produce the finished print.
Once actuated, the order of camera operations begins with exposure of a film unit or with automatic focusing which is thereafter followed by exposure of a film unit. Afterwards, the exposed film unit is advanced from its exposure position into engagement with a film processing subsystem or apparatus which initiates a diffusion transfer process for developing and forming a visible image in the film unit while transporting it to the exterior of the camera where it becomes accessible to the photographer.
The film units, as for example those described in considerable detail in U.S. Pat. Nos. 3,415,664; 3,594,165; and 3,761,268, normally contain all the photographic components necessary for the diffusion transfer process. Typically, the film units comprise, in general terms, a pair of superposed sheet elements, at least one being transparent, which serve to support layers of photochemical substances which may comprise photosensitive and image-receiving layers; and, as well, include a rupturable container of viscous processing fluid positioned adjacent a leading edge of the film unit and adapted to have its processing fluid released between the sheet elements to begin the diffusion transfer process. Release of the processing fluid is effected by the processing apparatus which first operates to rupture the container and thereafter causes the released mass of processing fluid to flow between the sheet elements, opposite the direction of travel of the film unit, so that the processing fluid is progressively deposited between the sheet elements as a thin, uniform layer generally coextensive with the exposed area of the film unit. Upon completion of the diffusion transfer process, the final image is viewable through the film unit sheet element which is transparent.
For optimum photographic image quality with film units utilizing this type of process, it is generally recognized that the thickness of the processing fluid layer must be substantially uniform and at least meet a minimum thickness requirement over the photoexposed area of the film unit. For example, the fluid layer thickness could nominally be a few thousandths of an inch with a tolerance of plus or minus a few ten-thousandths of an inch. Obviously fluid processing apparatus by which the thickness of the fluid layer over the photoexposed area of the film unit is controlled need to be manufactured to strict requirements in view of the tolerances imposed on the allowable variation in fluid layer thickness.
In general, the thickness of the processing fluid layer is a function of many variables which depend on the individual dimensions of the pieceparts which comprise the photographic processing apparatus and how the photographic processing apparatus interfaces with camera and film unit structure during the processing and transport stages. Examples of the many variables which can influence the thickness of the fluid layer include the magnitude of the compressive forces exerted on the film unit by processing rollers which form part of the fluid processing apparatus, the distance separating one processing roller from the other, the geometry, flexibility, and surface characteristics of the processing rollers, the viscosity of the processing fluid, the angle at which a film unit enters and exits the rollers, the physical characteristics of the photographic elements, and the speed at which the film unit is advanced between the rotating rollers.
Considering that such processing apparatus are structured of a number of pieceparts and that there are numerous variables which can effect the fluid layer thickness, it is understandable that it is a difficult task to properly manufacture such apparatus in view of the strict requirements imposed on their manufacture by the small tolerance variation allowed in the fluid layer thickness.
In order to meet the strict performance requirements imposed on such apparatus, one known practice in manufacturing fluid processing roller systems involves characterizing the geometry of the individual pieceparts which comprise the system and then assembling final systems on the basis of a piecepart match which will provide systems having optimum performance. Such a manufacturing process, however, requires carrying in inventory a number of spread rollers having different geometry which at present comprise about four groups which are used to accommodate variations in other pieceparts.
It is therefore a primary object of the present invention to provide a simplified method for manufacturing such fluid processing systems.
It is another object of the present invention to provide a method for manufacturing such fluid processing systems by which the necessity for carrying an inventory of rollers of different geometry can be eliminated.
It is another object of the present invention to provide a method for facilitating the assembly of such processing systems through the use of an adjustable electric discharge machining technique.
Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter. The invention accordingly comprises the method possessing the sequence of steps which are exemplified in the following detailed disclosure.